NEWBIE: for statement in "dive into python" gives syntax err

[Sean 'Shaleh' Perry]

On 23-Jul-2002 Mack wrote:
> Hi
> 
> I need some pointers. I've been reading the "Dive into python" tutorial
> and tried some statements on my machine. Redhat 7.1 with python 1.5.2
> 
>>>> li = [1, 9, 8, 4]
>>>> li
> [1, 9, 8, 4]
>>>> [elem*2 for elem in li]
>   File "<stdin>", line 1
>     [elem*2 for elem in li]
>               ^
> is what i'm getting. Is my python too old? Is something else wrong?
> I've just cut and pasted from the tutorial into python ide.
> 

yep.  "Dive Into Python" has a lot of code which only works under 2.1.x and up.
 The syntax you pasted is called a 'list comprehension' and was added in the
2.x series.

The 1.5 idiom for the above would have been:

output = map(lambda elem: elem * 2, li)

or

def double(item):
  return item * 2

output = map(double, li)

or even

output = []
for elem in li:
    output.append(elem * 2)